Device-to-Device Communications in Cellular System

ABSTRACT

The present invention provides a method and a controller to control not only cellular radio connections in a cell of a cellular communication system but also direct device-to-device communication links established between terminal devices within the cell. Particularly, the controller selects portion of the terminal devices to function as relay terminals for the other terminals to enable relayed communication links between the terminal devices and the base station through the relay terminals. The relay terminals link device-to-device connections to the cellular radio connections between the relay terminals and the base station.

FIELD

The invention relates to the field of cellular radio telecommunicationsand, particularly, to utilization of direct device-to-device connectionsin a cellular communication system.

BACKGROUND

Modern cellular telecommunication systems and terminals of such systemsare capable of supporting device-to-device communication capabilitiesfor efficient and cost-effective content delivery, network operation andperformance. Accordingly, two terminals located relatively close to eachother in the same cell may be configured by the network to communicateover a direct connection instead of routing the data through a cellularnetwork. It is even known that an ad hoc network among multiple terminaldevices may be formed based on the IEEE 802.11 standard, for example,and connections with the cellular network may utilize this ad hocnetwork to improve the overall coverage and performance of the cellularsystem. However, more efficient utilization of such ad hoc networkswould be advantageous from the viewpoint of the cellulartelecommunication system.

BRIEF DESCRIPTION

According to an aspect of the present invention, there is provided amethod as specified in claim 1.

According to another aspect of the present invention, there is providedan apparatus as specified in claim 16.

According to another aspect of the present invention, there is providedan apparatus as specified in claim 31.

According to yet another aspect of the present invention, there isprovided a computer program product embodied in a computer readabledistribution medium as specified in claim 32.

Embodiments of the invention are defined in the dependent claims.

LIST OF DRAWINGS

Embodiments of the present invention are described below, by way ofexample only, with reference to the accompanying drawings, in which

FIG. 1 illustrates communication links in a cell of a mobiletelecommunication system according to an embodiment of the invention;

FIG. 2 is a flow diagram illustrating a process for selecting andconfiguring relay terminals by a controller of a base station accordingto an embodiment of the invention;

FIG. 3 illustrates functional elements of the controller according to anembodiment of the invention;

FIG. 4 is a signaling diagram illustrating a procedure for establishinga relay link for a terminal device according to an embodiment of theinvention;

FIG. 5 illustrates elements of a relay-capable terminal according to anembodiment of the invention; and

FIG. 6 is a flow diagram illustrating a process for providing a relaylink in a relay-capable terminal according to an embodiment of theinvention.

DESCRIPTION OF EMBODIMENTS

The following embodiments are exemplary. Although the specification mayrefer to “an”, “one”, or “some” embodiment(s) in several locations, thisdoes not necessarily mean that each such reference is to the sameembodiment(s), or that the feature only applies to a single embodiment.Single features of different embodiments may also be combined to provideother embodiments.

FIG. 1 illustrates communication links in a cell 102 of a mobiletelecommunication system according to an embodiment of the invention.Referring to FIG. 1, the cell 102 is associated with a base station 100controlling communications within the cell. The cell 102 controlled bythe base station 100 may be divided into sectors, but such a scenario isnot illustrated in greater detail in order to keep the focus on theinvention. The base station 100 may control cellular radio communicationlinks established between the base station 100 and a plurality ofterminal devices 110 to 122 located within the cell 102.

As noted in the background section, device-to-device connections and adhoc networks may be established among the terminal devices 110 to 122.Let us now discriminate the cellular radio connections from thedevice-to-device connections by denoting that a cellular radiocommunication link established directly between a terminal device andthe base station 100 belongs to a first set of communication links. Thefirst set of communication links may be established and operatedaccording to a given radio standard supported by the mobilecommunication system of the base station 100. Such a standard may be along-term evolution of the UMTS (Universal Mobile TelecommunicationSystem), for example.

Furthermore, device-to-device communication links established directlybetween two terminal devices, e.g. between terminal devices 118 and 120in FIG. 1, belong to a second set of communication links. Thedevice-to-device connections may be based on cognitive radio technology.Accordingly, the terminal devices may be equipped with cognitive radiocapability to provide the device-to-device communication links accordingto any of a plurality of radio access technologies. Moreover, theterminal devices are equipped with a capability to adaptively select oneof the supported radio access technologies according to thecommunication environment. Such radio access technologies may includestandard and non-standard radio access technologies, e.g. Wireless LAN(IEEE 802.11), Bluetooth®, Ultra Wide Band. The radio accesstechnologies may operate on the same frequency band as the first set ofcommunication links and/or outside those frequency bands to provide thearrangement with flexibility.

According to an embodiment of the invention, the base station 100selects some of the terminal devices to function as relay terminals forthe other terminal devices so as to provide a relayed link between thenon-relay terminals and the base station 100. Only some of the terminals110 to 122 is selected as the relay terminals in order to establish ahierarchical or tree-type structure for the communication links and toprevent numerous links wasting communication resources and causingunnecessary interference. Referring to FIG. 1, the base station 100selects terminal devices 112 and 120 to function as the relay terminalsand configures the terminal devices 112 and 120 accordingly. The relayterminals may be selected according to environmental properties of theterminal devices and of the cell, allocated radio resources, etc., aswill be described below. When the terminal devices 112, 120 have beenconfigured and are ready to function as the relay terminals, they mayestablish communication links of the second set, i.e. cognitiveradio-based communication links, with the other terminal devices 110 to118, 122 to provide a link between the other terminal devices and thebase station 100. Referring to FIG. 1, the relay terminal 112establishes a communication link of the second set with terminal devices110 and 114 to provide the terminal devices 110 and 114 with a relayedlink to the base station. Similarly, the other relay terminal 120establishes a communication link of the second set with the terminaldevice 118. When establishing the relayed communication link, the relayterminal 112, 120 is configured to establish the communication link ofthe second set with a terminal device requesting the relayed linkaccording to a selected radio access technology, to negotiate with thebase station of the establishment of a cellular radio communication linkassociated with the relayed connection, i.e. associated with theterminal device requesting the relay, and to map the communication linkof the second set with the negotiated cellular radio communication link.The mapping may be carried out on a suitable protocol layer below theapplication layer, e.g. on a medium access control layer. Then, therelay terminal 112, 120 forwards data related to the negotiated cellularradio link and received from the base station to the communication linkof the second set and vice versa in order to forward data received fromthe non-relay terminal device to the base station and to forward datareceived from the base station and destined to the non-relay terminal tothe established communication link of the second set.

The base station may select and define which radio access technologiesshould be currently used for the communication links of the second set.The selection may depend on the utilization of the radio resources,properties of the communication environment, and properties of theselected relay terminals. Accordingly, the base station configures therelay terminals to provide only the communication links of the secondset. Furthermore, the base station may broadcast information indicatingthe selected radio access technologies to help the terminal devices toestablish communication links of the second set. For example, theterminal devices get knowledge about broadcast channels to scan whenattempting to establish a communication link of the second set.

Referring to FIG. 1, solid line signaling links (lines with arrows)indicate the communication links of the first set, i.e. directcommunication links between the base station and terminal devices,dashed lines indicate the communication links of the second set, i.e.direct communication links between terminal devices established withcognitive radio technology, and dotted lines indicate broadcastinformation broadcasted by the base station to facilitate theestablishment of the communication links of the second set. In additionto controlling only the communication links of the second set related tothe relayed links, and the regular cellular radio communication links,the base station 100 may also control radio access technologies used forthe device-to-device connections between two terminal devices not inneed of the cellular radio connection. This provides efficient radioresource management in the cell.

As mentioned above, the base station of the cellular mobiletelecommunication system controls both cellular radio connections, as inthe conventional system, and cognitive radio-based device-to-devicecommunication links to provide relayed connections between the basestation and the terminal devices. The control of the cognitive radiocommunication links may be embedded in radio resource control signalingof the cellular system. Accordingly, terminal devices that haveestablished a radio resource control (RRC) connection with the basestation may have their cognitive radio links controlled by the basestation. The control of the cognitive radio communication links may becarried out when a terminal device is either in an RRC idle state or inan RRC connected state. In an RRC idle state, the terminal device has noactive connection with the base station and no allocated radio resourcebut is capable of receiving RRC signaling information broadcasted by thebase station. In the RRC connected state, a radio resource controller ofthe base station has allocated radio resources to the terminal devicefor data transfer. Additionally, the terminal device may be directlyconfigured by the base station through RRC signaling. The RRC signalingmay be used to configure the radio access technologies and communicationparameters of the cognitive radio communication links.

FIG. 2 is a flow diagram illustrating a process for selecting andconfiguring relay terminals according to an embodiment of the invention.The process may be realized by a computer process executed in one ormore controllers (or processors) of the base station. The process startsin block 200.

In block 202, RRC connections with terminal devices are established. Theestablishment of RRC connections refers to configuring terminal devicesto RRC connected state. Not all the terminals located in the cellassociated with the base station are necessarily configured to the RRCconnected state, because some of the terminal devices may not have acurrent need for a data transfer connection.

In block 204, some of the terminal devices in the RRC connected stateare selected to function as the relay terminals. Several parameters maybe considered when selecting the relay terminals, such as capabilitiesof the terminal devices, radio resource utilization in the cell, batterypower of the terminal devices, traffic conditions of the terminaldevices, channel qualities experienced by the terminal devices,locations (distribution) of the terminal devices in the cell. The basestation may continuously receive measurement reports and otherinformation on the capabilities and properties of the terminal devices.The measurement reports may comprise channel quality reports receivedfrom terminals in the RRC connected state. Naturally, the base stationhas knowledge of the radio resources and traffic conditions of thecellular radio links of the terminal devices, because the base stationcontrols the radio resource management and traffic control for theterminal devices. In case the base station utilizes a distributedantenna system in the cell, the location of a given terminal may also bededuced on the basis of an antenna receiving the (strongest) signalsfrom the terminal device.

An algorithm may be executed in block 204 to consider the conditions ofthe terminal devices and the overall conditions of communication in thecell to select the most optimal selection of the relay terminals. Firstof all, the algorithm may estimate the number of relay terminals neededin the cell. The estimation may be carried out on the basis of trafficload in the cell and communication environment determined from themeasurement reports received from the terminal devices in the RRCconnected state. Then, the algorithm may carry out the actual selectionof the relay terminals.

The algorithm may select only terminals with cognitive radio capabilityas the relay terminals. Moreover, the algorithm may select a relayterminal to provide a terminal device hidden from the base station or inunfavorable conditions (poor channel conditions, low battery power,etc.) with a relayed communication link through the relay terminal. Thealgorithm may also consider the occupation of frequency bands allocatedto cellular radio communication links in order to determine whether touse radio access technologies utilizing the frequency bands of thecellular radio or other (unlicensed) frequency bands. Upon determinationof the frequency bands and radio access technologies utilized for thecommunication links of the second set (cognitive radio links), thealgorithm may select the terminal devices that support the selectedradio access technologies and discard those that do not. Then, thealgorithm may consider the current communication properties, e.g.

location, channel environment, traffic load, and battery power of theterminal devices. The algorithm may select the terminal devices that arein a good channel environment, have low traffic load, and good batterypower. The locations of the terminal devices may affect the selection insuch a way that the number of relay terminals selected from a specificarea in the cell is proportional to an estimated need for relayterminals in that area. For example, if a terminal is indicating a lowbattery in a specific area, a relay terminal may be established next tothat terminal so that a short-range relay link may be establishedbetween the terminal and the relay terminal, and the relay terminal maycarry out the long-range communication with the base station.

The algorithm may give determined weighting to the above-mentionedcriteria for the selection of the relay terminal. The algorithm may beexecuted periodically or continuously to adapt to the changing radioenvironment and to add new or remove relay terminals and to change radioaccess technologies and transmission parameters of the cognitive radiocommunication links used for the relaying connections. Alternatively,the algorithm may be triggered by a determined event in the cell, e.g.detection of several terminal devices in unfavorable conditions in agiven area.

Upon selection of the relay terminals, the selected relay terminals areconfigured to enable link relaying for the other (non-relay) terminaldevices. The configuration may comprise generating and transmitting tothe selected relay terminals a configuration message comprisinginformation on the selected radio access technologies for use as thecognitive radio communication links and parameters, such ascommunication parameters defining allocated resources, modulation andcoding schemes, diversity transmission schemes. The configurationmessage may configure the relay terminal to advertise to itssurroundings that it is available for provision of a relayed link to thebase station such that the other terminal devices detecting theadvertisement may establish a cognitive radio connection with the relayterminal. The advertisement may be realized by a broadcast of one ormore beacon signals according to the radio access technology ortechnologies selected by the algorithm and configured for use in therelay terminal. Additionally, the advertisement may indicate the basestation to which the relay terminal provides the relayed link.Accordingly, the advertisement may comprise an identifier of the basestation. The operation of the relay terminals is discussed in greaterdetail later.

FIG. 3 illustrates functional elements of the controller implementingthe process of FIG. 2. As mentioned above, the controller may controloperation and functionalities of the base station and communicationlinks in the cell associated with the base station. The controllercomprises an interface 306 to enable transmission and reception ofsignals and information related to the communication in the cell. Theinterface 306 may provide a connection to signal processing elements ofthe base station that perform signal processing necessary fortransmission and/or reception of a radio signal between the base stationand the terminal devices. Alternatively, the interface 306 may be asoftware interface to other software modules executed by the samephysical controller implemented by a digital signal processor, microcontroller, etc.

The controller further comprises a resource management module 304configured to handle management and allocation of cellular radioresources allocated to the base station by the mobile communicationsystem. The management of the cellular radio resources and theirallocation to the communication links of the first set may be carriedout according to any radio resource allocation scheme known in the art.In the context of the invention, it is advantageous for the efficientallocation of radio resources to the cognitive radio links to haveknowledge of the radio resources currently occupied by the cellularradio communication links.

The controller may further comprise a location and performancemanagement module 300. This module receives regular updates ofinformation on the communication properties of the terminal devices andthe radio channel. The location and performance management module 300may receive measurement reports from the terminal devices through theinterface 306, and additional information related to the locations ofthe terminal devices and their current communication properties. Thelocations of the terminal devices may be monitored with a positioningprocedure based on the analysis of handover measurement reports and/orseparate location reports received from the terminal devices. Theterminal devices may constantly monitor their locations with apositioning system, e.g. GPS, and inform the serving base station oftheir location. The positioning based on the analysis of the handovermeasurement results may be based on the candidate neighbor base stationlist of a terminal device, received signal strength associated with eachbase station, and known topology and environment of the cell, e.g.shadowed locations in the cell and shape of the cell and neighboringcells.

The controller further comprises a relay link controller 302 configuredto execute the selection algorithm described in connection with FIG. 2and to configure the selected relay terminals for providing thecognitive radio links to be used for relaying. The relay link controller302 is also configured to manage and reconfigure the relay terminals, ifnecessary. For example, a changing radio environment or traffic load inthe cellular communication links may cause a need to change the radioaccess technologies and/or parameters used for the cognitive radiolinks, to add new relay terminals or to cancel relaying of specificrelay terminals.

Instead of implementing the location and performance management module300 and the resource management module in the same controller as therelay link controller 302, the modules 300 and 304 may be implemented ina different controller, and the relay link controller 302 maycommunicate with the modules 300, 304 through the interface 306.

It has been described above that the terminal devices in the RRCconnected state may send the measurement reports to the base station. Inmobile cellular networks, the terminal devices in the RRC idle state donot send the measurement reports regularly. According to an embodimentof the invention, the base station may selectively configure and requesta cognitive radio-capable terminal device in the RRC, idle state to senda measurement report of the surrounding radio environment in the cellthe terminal device camps in to the base station in order to keep trackof the local-cell radio environment for cognitive radio networking. Themeasurement report may include relay terminals (and/or other cognitiveradio capable terminals) detected by the terminal device. Additionally,the measurement report may comprise an estimate of the quality of thechannel between the terminal device and each detected terminal device.In more detail, the base station may configure the terminal device byusing broadcast control signaling on, for example, a broadcast controlchannel or paging channel to carry out the measurements and to enter theRRC connected state to send the measurement report to the base station.The terminal device may send the measurement report through a directcellular connection with the base station or through a relayedconnection through a relay terminal. Upon transmission of themeasurement report, the terminal device may return to the idle state.This measurement reporting of cognitive radio-capable terminal devicesin RRC idle state may also be configured to be carried out along withregular mobility procedures of idle terminals, such as location updateprocedures.

In an embodiment, the base station may configure terminal devices in theRRC idle state to transmit a location update message indicating thelocation of the terminal device to the base station. The location updateof the idle terminals may be requested periodically. The base stationmay configure the terminal devices (or the terminal device may beconfigured) to transmit the location update message primarily through arelay link provided by a relay terminal. Accordingly, the terminaldevice does not have to enter the RRC connected state to transmit thelocation update.

FIG. 4 is a signaling diagram illustrating a procedure for establishinga relay link for a terminal device according to an embodiment of theinvention. The signaling diagram comprises signaling carried out betweenthe base station comprising the controller of FIG. 3, a first terminaldevice (terminal #1) in the RRC connected state with the base station,and a second terminal device (terminal #2) in the RRC idle state withthe base station.

In S1, the base station exchanges signaling information with theterminal devices. The base station receives channel quality informationand handover measurement reports from the first terminal device.Additionally, the base station allocates radio resources to the firstterminal device and a temporary identifier and corresponding controlinformation to the second terminal device. The temporary identifier of aterminal device in the RRC idle state may be refreshed or renewed uponregistration and/or location update of an idle terminal, as is known inthe art. Such a temporary identifier may be a paging token enabling thebase station to page the idle terminal device. Alternatively, theidentifier may be a fixed identifier, such as a radio frequencyidentifier (RFID) of the terminal device. The RFID may be a uniqueidentifier assigned to the terminal device in the manufacturing ortesting stage, and the terminal device may send its RFID to the cellularnetwork upon registration to the cellular network.

In S2, the base station decides to select the first terminal as a newrelay terminal. The decision may be based on the execution of thealgorithm described above with reference to block 204 of FIG. 2. In S3,the base station configures the first terminal to device-to-deviceoperation, i.e. to act as the relay terminal, as described above withreference to block 206 of FIG. 2 and FIG. 3. Accordingly, the basestation provides the first terminal with information comprisingnotification that the first terminal is to be used as the relayterminal, radio access technologies to be used for the device-to-devicecognitive radio connections used in connection with relaying, andtransmission parameters of such device-to-device connections. The basestation may also provide prioritization for the radio accesstechnologies to be used for the relayed connections. The base stationmay also configure the first terminal to advertise its availability asthe relay terminal in a specific manner, as will be described later inconnection with FIG. 6. The configuration of the first terminal devicemay be carried out as part of radio resource control signaling exchangedbetween the base station and the first terminal.

In S4, the base station broadcasts a broadcast signal comprising rulesand information of the device-to-device operation. The rules andinformation broadcasted by the base station may comprise general rulesto be applied to any communication link of the second set, i.e. even tothose not used for relayed connection. Thus, the base station mayprovide centralized control of all cognitive radio communication linksin the cell. Alternatively or additionally, the broadcasted informationmay comprise control information specific to relayed connections. Therules may comprise identification of radio access technologies to beused for relayed connections. The radio access connections may beprioritized so that one radio access technology is favored over another.The base station may also broadcast rules of utilization of the relayedlinks so that the terminal devices use the relayed connections in adesired manner. The base station may broadcast, for example, thresholdvalues for the quality of connection with the base station or withneighboring base stations to trigger utilization of the relayed link fora given terminal device when the quality of the cellular radiocommunication link drops below the threshold. The quality of thecommunication link may be measured from a carrier-to-interference ratio,for example.

The base station may broadcast the rules and information related to therelayed links on a broadcast control channel available to all terminaldevices in the cell, i.e. to those equipped with cognitive radiocapability and those not equipped with such capability. Alternatively,the base station may broadcast the rules and the information on achannel which is dedicated to terminal devices equipped with cognitiveradio capability. In a yet alternative embodiment, the base station maysend the rules and the information individually to each terminal deviceas part of radio resource control signaling. Accordingly, the terminaldevices capable of reading the rules and information may be in the RRCidle or RRC connected state.

In S5, the first terminal device configured as the relay terminaltransmits one or more beacon signals advertising its availability as therelay terminal. The relay terminal may broadcast beacon signals of thoseradio access technologies the base station has selected for use in therelayed links. The beacon signal broadcasted by the relay terminal maycomprise an identifier of the base station to indicate the base stationto which the relayed link is established. The base station identifiermay be a cell identifier identifying a cell associated with the basestation. Alternatively or additionally, the relay terminal may broadcasta cellular network identifier, e.g. a public land mobile network (PLMN)identifier, to indicate the cellular network to which the relayedconnection is provided. The beacon signal also comprises an identifierof the relay terminal. The identifier may be a temporary cellular radioidentifier assigned by the base station (or another element of thecellular mobile telecommunication system) and, as a consequence, therelay terminal uses the same identifier for the cellular radioconnection with the base station and for the direct device-to-deviceconnections with the other terminal devices, for which the relayterminal establishes the relayed connection. The identity of thecellular network is used for the relayed connections for security,uniqueness, and protocol overhead deduction purposes. The temporaryidentifier of the relay terminal may be, for example, a 16-bitcell-specific radio network temporary identifier (C-RNTI) known in theUMTS.

Instead of providing explicit information on the availability of therelayed communication link, the relay terminal may indicate theavailability of the relay connection implicitly by broadcasting specificconnection-related information in the beacon signal in order to let theother (non-relay) terminals determine the suitability of the relayedconnection. The implicit information should naturally be in line withthe information and rules broadcasted by the base station in S4, becausethe non-relay terminals receive both information and rules broadcastedby the base station in S4 and implicit information broadcasted by therelay terminal in S5. Such information may comprise information on atleast one of data rate, transport block sizes, frequency resources, atransmission power supported by the relay terminal for each radio accesstechnology utilized for the relayed connection. At least some of theparameters may be defined by the base station in S3. Additionally, suchinformation may comprise information on the radio environmentexperienced by the relay terminal.

In S6, the second terminal device detects the beacon signal broadcastedby the first terminal device. The second terminal device may havereceived the rules and information broadcasted by the base station in S4and configured itself to scan for beacon signals of the radio accesstechnologies indicated by the base station. Upon detection of the beaconsignal from the first terminal device and determination that a relayedconnection is necessary, e.g. due to a shadowed direct link with thebase station, the second terminal negotiates a device-to-devicecommunication link with the first terminal according to one of the radioaccess technologies based on the cognitive radio. The first and secondterminals may use the identifiers described above in -thedevice-to-device communication link. The type of identifiers useddepends on the implementation. In one embodiment, both terminal devicesuse RFIDs. In another embodiment, the first terminal being in the RRCconnected state uses C-RNTI, and the second terminal device being in theRRC idle state uses the paging token previously received from thecellular network. Upon negotiation of the device-to-device communicationlink of the second set between the terminal devices #1 and #2, the firstterminal device negotiates with the base station that it will functionas a relay between the base station and the second terminal device.

If the cognitive radio communication link between the terminal devicesis established as a Bluetooth link or corresponding communication linknormally requiring acceptance of a user to establish the communicationlink, the acceptance by the user may be replaced by an acceptance by thebase station. Accordingly, if the second terminal device requests aBluetooth communication link with the first terminal device, the firstterminal device negotiates the request with the base station, and thebase station approves the communication link. As a consequence, thesecond terminal device now has a communication link with the basestation through the first terminal device.

FIG. 5 illustrates radio communication elements of a relay-capableterminal device according to an embodiment of the invention. First ofall, the terminal device comprises radio interface components 506capable of providing radio communication parameters according to thephysical layer protocols of one or more cellular telecommunicationsystems supported by the terminal device. Additionally, the radiointerface components 506 may be configured to provide radiocommunication parameters according to a plurality of device-to-deviceradio communication protocols, e.g. one or more of the radiocommunication protocols listed above. The radio interface components 506may include digital signal processing elements capable of providingmultiple modulation, coding, and other signal processing operations onthe base band for signals to be transmitted and/or received.Additionally, the radio interface components may comprise analogcomponents, of which at least part may be software-defined to providesupport for the wide range of radio access technologies.

The terminal device further comprises a higher-level controller 500controlling the operation and inter-operability of both communicationlinks of the first set (the cellular radio communication links with theserving base station and other parts of the serving cellular network)and the communication links of the second set (the cognitive radiocommunication links with other terminal devices). The communicationcontroller 500 may provide linking between the cognitive radioconnections and the cellular radio connections to provide the relayedlink.

The communication controller 500 comprises two sub-controllers: acognitive radio communication controller 502 and a cellular radiocommunication controller 504. The cellular radio communicationcontroller 504 is configured to establish, operate, and terminatecellular radio connections with a serving base station of a servingcellular network. The cellular radio communication controller 504 mayalso convey data and control signals related to the cognitive radiocommunication links under the control of the higher-level communicationcontroller 500. The communication controller 500 may communicate withthe serving base station through the cellular radio communicationcontroller 504 in order to negotiate radio access technologies for usein direct device-to-device communications with the other terminaldevices in the same cell, communication parameters to be used, and themethod of advertising the availability of the relayed communicationlink. The negotiation may comprise indicating the capabilities of theterminal device to the base station and reception of the configurationfrom the base station. For example, the communication controller 500 maycommunicate to the base station which radio access technologies,frequency bands and other communication parameters the terminal devicesupports. The base station may then select the configuration accordingto the capabilities of the terminal device and other factors, asdiscussed above in connection with FIG. 2.

The cognitive radio communication controller 502 is configured toestablish, operate, and terminate cognitive radio connectionsestablished with the other terminal devices. The cognitive radiocommunication controller 502 may receive the radio access technologiesand communication parameters available for use from the communicationcontroller 500 and control the radio interface components 506 tobroadcast one or more beacon signals to indicate the availability of therelayed connection to the other terminal devices. Upon reception of arequest to establish a cognitive radio communication connection fromanother terminal device through the radio interface components 506, thecognitive radio communication controller 502 may be configured to firstdetermine whether the request is a normal device-to-device communicationrequest or a request for the provision of the relayed communicationlink. If the provision of the relayed communication link is requested,the cognitive radio communication controller 502 may indicate this tothe communication controller 500 which may negotiate with the servingbase station about the establishment of the relayed communication linkand provide linking between the cognitive radio communication link andthe cellular radio communication link. The establishment of the relayedcommunication link may include the establishment of a new logicalconnection between the relay terminal and the serving base station.Accordingly, the communication controller 500 may negotiate with theserving base station of the establishment of the new logical connectionthrough the cellular radio communication controller.

Then, the cognitive radio communication controller 502 may determine thecommunication parameters to be used in the cognitive radio communicationlink on the basis of the available communication parameters and thechannel environment between the two terminal devices. The cognitiveradio communication controller may negotiate the communicationparameters to be used with a corresponding cognitive radio communicationcontroller in the other terminal device. The determination of thecommunication parameters may include the determination of modulation andcoding schemes, frequency band, bandwidth, data rate, transport blocksize, diversity method, etc.

The procedure may be the same in the case of a normal device-to-devicecommunication link except that the provision of the linking between thecognitive radio connection and the cellular connection may be omitted.Furthermore, negotiation between the communication controller 500 andthe serving base station may also be omitted, because the communicationcontroller 500 may already have all the necessary information for theestablishment and operation of the device-to-device connections.

Upon establishment of the relayed communication link through the relayterminal, the communication controller 500 receives data from the otherterminal device, for which the relaying is performed, through thecognitive radio communication controller 502 and maps the data to thelogical connection established between the communication controller 500and the serving base station. Similarly, the communication controllermaps the data received from the serving base station over theestablished logical connection to the cognitive radio connection.

FIG. 6 is a flow diagram illustrating a process for providing a relaylink in a relay-capable terminal device according to an embodiment ofthe invention. In particular, FIG. 6 illustrates the operation of theelements of

FIG. 6. The process starts in block 600, and the relay terminalestablishes the RRC connection with the base station in block 602. Therelay terminal may be configured to be in the RRC connected state. Inblock 604, the relay terminal transmits measured environment-relatedinformation to the base station. The measured information may compriseone or more estimates of the communication channel, measurement resultsof received signal strengths associated with the serving base stationand other base stations, measured location of the terminal device in thecell, measured battery power, etc.

In block 606, the relay terminal receives from the serving base stationa device-to-device relay functionality configuration. The relay terminalmay also use the same configuration for the other device-to-devicelinks. As mentioned above, the configuration information may alsocomprise configuration of the type of beaconing the terminal device isto use when indicating to the other terminals of the availability of therelayed link.

In 608, the relay terminal broadcasts one or more beacon signalscomprising information either on explicit or implicit availability ofthe relayed link. In block 610, it is determined whether or not therelay terminal receives a connection request from another terminaldevice. If not, the process returns to block 608. Otherwise, the relayterminal is determined to have received the connection request fromanother terminal device, The connection request may be a regulardevice-to-device connection request or a request to establish a relayedlink to the serving base station. The request to establish the relayedlink may be a request to establish a data connection or only a controlsignaling connection.

In block 612, the device-to-device communication link is establishedbetween the relay terminal and the other terminal device and related newlogical connection with the base station, and data between thedevice-to-device link and the cellular link is forwarded in block 614.The relay terminal may establish either a data connection or only acontrol connection with the serving base station. In connection ofestablishment of the data connection, the control connection is alsoestablished, but the control connection may be established without thedata connection. The idea behind the establishment of only the controlconnection is to receive information on transmission timings related tocognitive radio connections operating on the same frequency band as thecellular radio connections. Then, the terminal devices operating suchcognitive radio connections may adjust their transmission timings suchthat the cognitive radio transmission does not interfere with thecellular radio connections. In other words, the timing information maybe used to synchronize the terminals to the clock of the base station.Alternatively, the relay terminal may broadcast the timing informationin block 608 either as an absolute timing or as a timing offset to aclock of the relay terminal. The reference time of the relay terminalmay also be broadcasted. Alternatively, the time reference may bededuced from the frame structure on the signal received from the basestation.

Additionally, the control signaling connection may be used to relayconnection establishment information to the terminal device through therelay terminal. For example, the base station may transmit a dedicatedrandom access channel preamble allocation or other correspondinginformation to the terminal device via the relay terminal to enable theterminal device to establish a direct communication link with the basestation. Upon reception of the random access channel preamble orcorresponding control information from the relay terminal, the terminaldevice may initiate a contention-free random access procedure toestablish a connection with the base station more reliably.

The processes or methods described in FIGS. 2 and 6 may also be carriedout in the form of a computer process defined by a computer program. Thecomputer program may be in source code form, object code form, or insome intermediate form, and it may be stored on a carrier, which may beany entity or device capable of carrying the program. Such carriersinclude a record medium, computer memory, read-only memory, electricalcarrier signal, telecommunication signal, and software distributionpackage, for example. Depending on the processing power needed, thecomputer program may be executed in a single electronic digitalprocessing unit or it may be distributed amongst a number of processingunits.

It will be obvious to a person skilled in the art that, as technologyadvances, the inventive concept can be implemented in various ways. Theinvention and its embodiments are not limited to the examples describedabove but may vary within the scope of the claims.

1-32. (canceled)
 33. A method comprising: receiving a configurationmessage by a first terminal device in a first communication link from abase station, where the configuration message comprises informationelements for enabling the first terminal device to operate as a relayterminal between a second terminal device and the base station, wherethe information elements of the configuration message indicate whichradio access technology or technologies is to be used for a secondcommunication link between the first terminal device and the secondterminal device; and transmitting by the first terminal device to thesecond terminal device at least one message comprising informationindicating to the second terminal device that the first terminal deviceis available as a relay terminal between the second terminal device andthe base station, where the information indicating to the secondterminal device that the first terminal device is available as the relayterminal comprises an identifier of the first terminal device and anidentifier of the base station.
 34. A method as in claim 33 where theidentifier of the base station is a cell identifier which identifies acell associated with the base station.
 35. A method as in claim 33 wherethe at least one message is transmitted on at least one of the radioaccess technology or technologies to be used for the secondcommunication link.
 36. A method as in claim 33 where the informationcomprises a cellular network identifier.
 37. A method as in claim 33where the information comprises at least one of data rate, transportblock sizes, frequency resources, a transmission power supported by thefirst terminal device for each radio access technology utilized for arelayed connection.
 38. A method as in claim 33 where the at least onemessage comprises at least one beacon signal advertising availability ofthe first terminal device as the relay terminal.
 39. A method as inclaim 38 where the configuration message comprises information regardinga configuration of a type of beaconing to be used by the first terminaldevice for the at least one beacon signal.
 40. A method as in claim 38where the information in the at least one beacon signal comprisesinformation on implicit availability of the second communication link asa relay link.
 41. A method as in claim 33 further comprising receivingrules and information by the first terminal device, from the basestation, related to the second communication link being used as a relaylink on a channel which is dedicated to terminal devices equipped withcognitive radio capability.
 42. An apparatus comprising: at least oneprocessor; and at least one non-transitory memory including computerprogram code, the at least one memory and the computer program codeconfigured to, with the at least one processor, cause the apparatus to:upon receiving a configuration message by the apparatus in a firstcommunication link from a base station, where the apparatus comprises afirst terminal device, determining which radio access technology. ortechnologies is to be used for a second communication link between thefirst terminal device and a second terminal device, where theconfiguration message comprises information elements for enabling thefirst terminal device to operate as a relay terminal between the secondterminal device and the base station, and where the information elementsof the configuration message indicate which radio access technology ortechnologies is to be used for the second communication link; andtransmit by the first terminal device to the second terminal device atleast one message comprising information indicating to the secondterminal device that the first terminal device is available as a relayterminal between the second terminal device and the base station, wherethe information indicating to the second terminal device that the firstterminal device is available as the relay terminal comprises anidentifier of the first terminal device and an identifier of the basestation.
 43. A non-transitory program storage device readable by amachine, tangibly embodying a program of instructions executable by themachine for performing operations, the operations comprising: receivinga configuration message by a first terminal device in a firstcommunication link from a base station, where the configuration messagecomprise information elements for enabling the first terminal device tooperate as a relay terminal between a second terminal device and thebase station, where the information elements of the configurationmessage indicate which radio access technology or technologies is to beused for a second communication link between the first terminal deviceand the second terminal device; and transmitting by the first terminaldevice to the second terminal device at least one message comprisinginformation indicating to the second terminal device that the firstterminal device is available as a relay terminal between the secondterminal device and the base station, where the information indicatingto the second terminal device that the first terminal device isavailable as the relay terminal comprises an identifier of the firstterminal device and an identifier of the base station.
 44. A methodcomprising: receiving by a second terminal device, from a first terminaldevice, at least one message comprising information indicating to thesecond terminal device that the first terminal device is available as arelay terminal between the second terminal device and the base station,where the information indicating to the second terminal device that thefirst terminal device is available as the relay terminal comprises anidentifier of the first terminal device and an identifier of a basestation, and where the information indicates which radio accesstechnology or technologies is to be used for a communication linkbetween the first terminal device and the second terminal device; andtransmitting a connection request from the second terminal device to thefirst terminal device via the indicated radio access technology ortechnologies.
 45. An apparatus comprising: at least one processor; andat least one non-transitory memory including computer program code, theat least one memory and the computer program code configured to, withthe at least one processor, cause the apparatus to: upon receiving bythe apparatus, from a first terminal device, at least one messagecomprising information indicating to the apparatus that the firstterminal device is available as a relay terminal between the apparatusand the base station, where the information indicating to the secondterminal device that the first terminal device is available as the relayterminal comprises an identifier of the first terminal device and anidentifier of a base station, and where the apparatus is a secondterminal device and where the information indicates which radio accesstechnology or technologies is to be used for a communication linkbetween the first terminal device and the second terminal device,determining which of the radio access technology or technologies is tobe used for the communication link between the first terminal device andthe second terminal device; and transmit a connection request from thesecond terminal device to the first terminal device via the indicatedradio access technology or technologies.
 46. A non-transitory programstorage device readable by a machine, tangibly embodying a program ofinstructions executable by the machine for performing operations, theoperations comprising: receiving by a second terminal device, from afirst terminal device, at least one message comprising informationindicating to the second terminal device that the first terminal deviceis available as a relay terminal between the second terminal device andthe base station, where the information indicating to the secondterminal device that the first terminal device is available as the relayterminal comprises an identifier of the first terminal device and anidentifier of a base station, and where the information indicates whichradio access technology or technologies is to be used for acommunication link between the first terminal device and the secondterminal device; and transmitting a connection request from the secondterminal device to the first terminal device via the indicated radioaccess technology or technologies.
 47. A method comprising: selecting afirst terminal device to be used as a relay terminal; transmitting by abase station a configuration message to the first terminal device in afirst communication link, where the configuration message comprisesinformation elements for enabling the first terminal device to operateas the relay terminal between a second terminal device and the basestation, where the informational elements are configured to beretransmitted by the first terminal device to the second terminal deviceand comprise an identifier of the base station indicate which radioaccess technology or technologies is to be used for a secondcommunication link between the first terminal device and the secondterminal device.
 48. A method as in claim 47 where the identifier of thebase station comprises a cell identifier identifying a cell associatedwith the base station.
 49. An apparatus comprising: at least oneprocessor; and at least one non-transitory memory including computerprogram code, the at least one memory and the computer program codeconfigured to, with the at least one processor, cause the apparatus to:select a first terminal device to be used as a relay terminal; andtransmit by the apparatus a configuration message to the first terminaldevice in a first communication link, where the apparatus is a basestation, where the configuration message comprise information elementsfor enabling the first terminal device to operate as the relay terminalbetween a second terminal device and the base station, where theinformational elements are configured to be retransmitted by the firstterminal device to the second terminal device and comprise an identifierof the base station and indicate which radio access technology ortechnologies is to be used for a second communication link between thefirst terminal device and the second terminal device.
 50. An apparatusas in claim 49 where the identifier of the base station comprises a cellidentifier identifying a cell associated with the base station.
 51. Anon-transitory program storage device readable by a machine, tangiblyembodying a program of instructions executable by the machine forperforming operations, the operations comprising: selecting a firstterminal device to be used as a relay terminal; and transmitting by abase station a configuration message to the first terminal device in afirst communication link, where the configuration message compriseinformation elements for enabling the first terminal device to operateas the relay terminal between a second terminal device and the basestation, where the informational elements are configured to beretransmitted by the first terminal device to the second terminal deviceand comprise an identifier of the base station and indicate which radioaccess technology or technologies is to be used for a secondcommunication link between the first terminal device and the secondterminal device.
 52. A non-transitory program storage device as in claim51 where the identifier of the base station comprises a cell identifieridentifying a cell associated with the base station.